The present invention relates to automotive gaskets, particularly to non-stick automotive gaskets and more particularly to gaskets which contain polymeric fluorocarbons on their surfaces to impart non-stick properties thereto.
Gaskets have been used to provide a seal between two engaging or mating parts. For example gaskets have been employed in internal combustion engines such as automobile and diesel engines. In these engines there is a need for gaskets which are adapted to be mounted between the engine head and block. These gaskets have a plurality of cylinder holes, a plurality of stud holes and a plurality of lubricant and coolant holes. These gaskets are held under compression between the cylinder block and a cylinder head and insures against leakage of fluids such as oil and coolant.
When these gaskets begin to deteriorate over a period of time, the oil and coolant will begin to leak around the holes for the oil and coolant and cause further corrosion of the gasket. Once a gasket begins to deteriorate, it is necessary to remove the gasket and insert a new gasket. Oftentimes, the gasket will disintegrate when the engine head and block are separated and parts of the gasket will adhere to the mating surfaces of each. It is often difficult to remove parts of the gasket from the engine head and block and generally, each of the mating surfaces have to be scraped in order to remove the gasket residue.
Gaskets having asbestos fibers and synthetic rubber on their upper and lower surfaces have been treated with polysiloxanes and silicone oil to help eliminate the tendency of the asbestos fibers to adhere to the respective opposite metallic surfaces of the cylinder head and the engine block. For example. U.S. Pat. No. 4,483,539 to Bindel et al discloses a head gasket having a plate of soft material which is first treated with a polysiloxane having a tendency to react with the OH groups of the asbestos fibers. A polysiloxane resin is then applied to the soft material and the soft material heated to polymerize the polysiloxane.
U.S. Pat. No. 4,826,708 to Udagawa discloses applying a seal coating to a base plate of a gasket. The seal coating may be a fluorocarbon polymer, a silicone polymer or a silicone gum.
U.S. Pat. No. 4,103,913 to McDowell discloses a metal gasket having a sealing bead of silicone sealant deposited on the top and/or bottom surfaces and at a position closely adjacent to the peripheral edges of the gasket body. Subsequent to the application of the silicone bead, the gasket body is coated at positions remote from the silicone bead with a mixture containing molybdenum disulfide and polytetrafluoroethylene.
U.S. Pat. No. 4,169,185 to Bhatia discloses a gasket consisting of a metallic base sheet having a sealant coating thereon consisting of a heat-cured, phenyl-substituted, hydrocarbyl-substituted polysiloxane resin having metallic powder dispersed therein.
It has been found that gaskets treated with silicone materials still have a tendency to adhere to the respective opposite metallic mating surfaces of an automotive internal combustion engine.
Therefore, it is an object of the present invention to provide gaskets which exhibit release properties from the respective metallic mating surfaces. Another object of the present invention is to provide gaskets having an improved seal to the respective metallic mating surfaces. A further object of the present invention is to provide a gasket having greater durability or stability. A still further object of the present invention is to provide a gasket having substantially higher temperature stability which results in an improved seal of the gasket surface.